The present invention relates to a method of leaching of metal sulphide-containing material which contains one or more metal sulphides of the metals iron, copper, lead, silver, mercury and zinc and aims particularly at leaching of sulphide ores, which besides copper also can contain one or more of the above mentioned metal sulphides together with other valuable metals for the purpose of recovering the metal values.
The leaching is effected by means of chloride-containing solutions according to the red-ox principle by treating the metal sulphide-containing material with a solution which chiefly consists of bivalent copper (cupric) chloride and threevalent iron (ferric) chloride, where the metals are brought into solution as metal chloride, which can be recovered from the solution. The metal-containing solution is conducted to recovery processes for recovery of the separate metals. During the leaching process the originally bivalent copper (cupric) chloride and the threevalent iron (ferric) chloride are reduced to respectively monovalent copper (cuprous) chloride and bivalent iron (ferrous) chloride which are subsequently reoxidized to bivalent copper chloride and threevalent iron chloride by a regeneration process, whereupon the regenerated liquor is used again in the process. For metal recovery processes such as electro recovery of copper, liquid-liquid extraction of zinc and other processes, it is of advantage and in some cases absolutely necessary that the leach liquor is maximally reduced to bivalent iron and monovalent copper.
Several methods for leaching of metal sulphide-containing material are known, but these processes have the drawback that they do not secure a combination of such maximum reduction and complete leaching of the metal values in the raw material. The known methods do not specify why a complete reduction is not obtained, but it is to be assumed that in practical operation, because of the variations in the composition of the metal sulphide-containing material and the regenerated leach liquor, it is very difficult to proportionate in such a way that the process can be carried out under complete stoichiometry in order to obtain the required combination of complete leaching and complete reduction.